The present invention relates to a system and a method for establishing a telecommunication connection and transferring calls in a telecommunication network and a data transfer network. The invention further relates to a mobile station comprising connecting means for establishing a telecommunication connection and transferring information between the mobile station and said telecommunication network and data transfer network.
In modern office work it is necessary to provide the employees with versatile information transfer connections which can transfer speech, facsimile messages, electronic mail and other dataxe2x80x94usually in digital form. Transfer of information is needed inside an office or corresponding working environment for communication between employees, for transfer of information between branch offices of an enterprise, which offices can be in other towns or even in other countries, and for communication between the office and xe2x80x9coutside worldxe2x80x9d. In this text and all of the following text xe2x80x9cofficexe2x80x9d stands for an environment with several users, which users xe2x80x9cbelong togetherxe2x80x9d, and which office physically covers a reasonably limited area. There has been a trend in the telecommunication branch toward integrated systems in which various forms of telecommunication can be controlled as one entity.
A conventional realization of an above mentioned type of office communication system comprises in order to provide telephone services a company telephone exchange and telephones connected to it typically over twisted-pair connections and a separate local area network (LAN) in which applications for advanced telecommunication services have been implemented and which has the intelligence to run them. The local network is connected to the telephone exchange using a telecommunication server (Telephony Server) which supports the traditional subscriber server architecture in which subscribers are subscribers"" computers connected to the local network. For example call-, data-, facsimile-, electronic mail- and speech mail services are connected within an office utilizing the telecommunication server. In an integrated system users can also e.g. control telephone services using their computer terminals connected to the local network. The whole integrated office communication system is connected to public telephone network through the telephone exchange.
FIG. 1 presents an example of a prior known office communication system in which users"" telephones TP (TelePhone) have been connected by wire connections and a local area network (LAN) has been connected over a telecommunication server TS (Tele Server) into a telephone exchange PBX (Private Branch Exchange) which is connected to a public telephone network PSTN/ISDN (PSTN, Public Switched Telephone Network, ISDN, Integrated Services Digital Network). To the local area network (LAN) have been connected on one hand servers executing various services such as data base server DBS (Data Base Server), voice server VS (Voice Server) and electrical mail server EMS (Electrical Mail Server) and on the other hand the users"" computers PC (Personal Computer). It can be regarded as a problem with this kind of realization that even if a user""s telephone TP and computer PC usually are on the same table next to each other separate wire connections must be laid to the user""s working room for them, on one hand from the telephone exchange PBX and on the other hand from the telecommunication server TS of the LAN. Building and maintenance of two overlapping telecommunication networks naturally causes cost.
The problem of overlapping telecommunication networks is increased by portable mobile stations utilizing radio connection coming rapidly more popular. Many persons working in an office need, because of their mobile work, a mobile station and often also a combination of a portable computer and a mobile station capable of sending and receiving facsimile messages and E-mail. It is also possible to integrate the above equipment into a so called multiservice mobile station, as an example of which can be mentioned Nokia Communicator 9000. In order to be able to use these devices based on radio connection also inside buildings, the constructions of which attenuate radio signals, it has been suggested that mobile radio networks should be supplemented with small base stations individual for offices or even for rooms, which base stations would be connected either directly or over wired telephone network to the central systems of mobile communication network. The network of small base stations would be already a third overlapping telecommunication network within the same office, and accordingly it is clear that in a preferable solution, which the present invention is aiming at, also the arrangement supporting radio communication stations should be realized using essentially the same means and telecommunication networks than the rest of the transfer of information in the office.
A challenge of its own to telecommunication systems is issued by the fact that work is done more and more in small-office or domestic environment, which is described by the concept SOHO (Small Office, Home Office). Even here advanced office communication services are often needed and it is particularly preferable if such a flexible system is available which can be utilized even both in the office and at home. The present systems which require overlapping connections for the utilization of mobile communication services, conventional telephone services and fast data transfer services are very inflexible for working in a small- or home office. In addition to above, the following kinds of solutions connected with integrated telecommunication systems are known from prior art.
EP publication 599 632 presents a wireless local network designed to replace the present kind of wired local networks (e.g. registered trade marks Ethernet and Token Ring) by a radio transfer network which forms inside an enterprise a private cellular system designed for data transfer. A network utilizing radio connection is, however, relatively expensive to realize and it is more sensitive to interference than a local network based upon wired connections. In addition to that it requires establishing of an extra radio network in addition to previous networks.
EP publication 462 728 presents an intelligent base station controller, subordinated to which at least one radio communication system base station is operating and which is capable of connecting calls from a certain mobile station coming through the base station directly to wired telephone network. This system, however, requires said additional base stations, which increases the cost. The system is also, alike the system presented in publication 599 632, sensitive to external (radio)interference.
If an integrated office communication system is realized utilizing traditional technique, separate wired connections must be laid into a user""s working room on one hand from telephone exchange PBX (FIG. 1) and on the other hand from telecommunication server TS of local area network (LAN). Constructing and maintaining two overlapping networks naturally brings extra cost. In said solutions according to prior art a solution to this problem has not actually been striven for.
It is possible to install so called Internet-phone software in computers connected to the nowadays very popular Internet-network. They facilitate the transferring of speech between two computers. Software is available for downloading among other things through the Internet-network as so called Share-Ware software, and their spectrum is wide. They utilize as a user interface the monitor of the computer and an audio card equipped with audio interfaces installed in the computer, and a loudspeaker and a microphone, either separate or integrated in the monitor of the computer. A big problem with these systems is the lack of standardization, i.e. most of the available software is only capable of communicating with another identical software. In said Internet-phone software the speech encoding and decoding are carried out in computers, and accordingly the computers are heavily loaded and the simultaneous running of other programware is disturbed or in the worst case entirely impeded. Internet-phone softwares are fully tied to a local network and to the computer in which they are installed, and accordingly they are not suited for portable operation.
The target of the present invention is to present a flexible system which reduces the problems caused by overlapping networks. Additionally, the purpose of the invention is to reduce problems caused by wireless information transfer inside an office and extra cost. A further target of the invention is to present an arrangement, in which said system, integrating information transfer, can also serve home office- and small office users. A further target of the invention is to present an arrangement of said kind, in which the same devices can be used as terminal devices in the telecommunication system equally well while connected to telecommunication networks realized using line connections in an office as wirelessly outside the office.
Now a system has been invented for transfer of information, e.g. speech or data, in which the trunk of information transfer is inside the office a local network (e.g. local area network (LAN)), and between office units e.g. a data transfer connection (e.g. an Internet-connection realized using ISDN-lines) utilizing traditional line connections or a fast data packet network utilizing ATM (Asynchronous Transfer Mode) technique. In an information transfer system according to the invention the services normally provided by a telephone exchange and a telephone network have been moved into connection with a local network. As a terminal device in the system it is used a mobile station according to the invention, which operates like a normal mobile station when disconnected. Incoming and outgoing calls are routed by radio based upon the phone number of the mobile station. If the mobile station according to the invention is connected to a system according to the invention, the transferring of calls is moved to be performed over the local network. In this case it is possible to switch off the radio frequency parts of the mobile station according to the invention.
A mobile station according to the invention is connected to a system over a terminal device, typically a computer. The mobile station comprises a separate identification information, based upon which calls are routed while the mobile station is connected to the system according to the invention. Preferably the IP (Internet Protocol)-address of a user""s own computer is used as the identification information. Also any other communication address referring to the particular computer may be used. The information transfer within the network is realized using e.g. the TCP/IP (Transmission Control Protocol/Internet Protocol)-protocol prior known to a person skilled in the art.
In a call transfer system according to the invention a network server has been arranged in connection with a mobile telephone exchange, through which server calls intended to a mobile station according to the invention are routed over an interconnecting network, a local area network and a terminal device further to the mobile station, provided that the mobile station is not connected to the mobile communication network by radio. To a mobile telephone exchange the network server and the mobile stations according to the invention connected through it form an interface (e.g. in the GSM-system the A-interface) corresponding with a base station controller, and accordingly no changes need preferably be made in the mobile telephone exchange. The network server emulates a base station controller including signalling. The connecting to or disconnecting from to the mobile communication network through the terminal device, the local area network, the interconnecting network and the network server thus correspond with a handover prior known to a person skilled in the art. The above mentioned routing is facilitated by a database arranged in connection with the network server, in which database it is stored the identification information (e.g. a IP-address) defined for the telephone number of each mobile station according to the invention. The network server also answers for the protocol conversions, prior known to a person skilled in the art, from a circuit switched telephone network to e.g. a packet-switched interconnecting network and vice versa. When a mobile station according to the invention is connected to a terminal device, an application program executed in the terminal device polls the identification (IPxe2x80x94address) of the xe2x80x9cownxe2x80x9d terminal device of mobile station stored in the mobile station and compares it with its own one. If the IPxe2x80x94addresses match, the terminal device knows that the connected terminal device is an xe2x80x9cownxe2x80x9d terminal device. In this case both incoming and established calls are transferred based upon the information contained in a database.
If a mobile station according to the invention is connected to a system via a terminal device other than the own computer of the user of the mobile station, the address (IPxe2x80x94address) of the local network in the database situated in connection with a network server no longer corresponds with the real location of the mobile station. In such a case the IPxe2x80x94address contained in the database must be updated to correspond with the real location of the mobile station. It is possible to realize this e.g. by sending to the network server an update-message comprising the identification (IPxe2x80x94address) of the connected mobile station and the IPxe2x80x94address of the computer which it at the moment is connected to.
In a preferable embodiment of the invention the database in connection with a network server need not be updated, but routing is realized using another principle. When the application program running in a terminal device detects that a connected mobile station is a xe2x80x9cvisitingxe2x80x9d one, it transmits a routing message to the xe2x80x9cownxe2x80x9d terminal device of the visiting mobile station. Based upon the routing message the own terminal device of the visiting mobile station routes incoming calls to the mobile station to the new address. When the visiting mobile station is disconnected from the terminal device, the latter transmits a cancellation message to the own terminal device of the mobile station.
Traditional telephones have been replaced with mobile stations according to the invention, which, while in the office, are connected either using a cable, an infrared connection, or low-power radio transceivers. In this case the traditional radio frequency parts of the mobile station are switched off in a way characteristic of the invention and the mobile station is connected to a data network and through it further to a telecommunication network through a terminal device and a local area network. In this case the mobile station does not contact the telecommunication network using radio frequencies, not loading the mobile communication network, the possibly poor network coverage inside the building does not reduce the quality of the connection, and no cost for using the mobile communication network radio channels is involved.
It is also possible to use the call transfer system according to the invention according to another principle. If the radio frequency parts of the mobile station are not switched off and the radio connection to a mobile communication network is maintained as normal, the connection to a local area network and through it to e.g. Internet-network can be examined exclusively from the point of view of connecting additional services. Accordingly a call transfer system according to the invention facilitates among other things the use of a mobile station as an Internet-telephone without losing the accessibility through a traditional mobile communication network.
A system and method for call transfer according to the invention and a mobile station according to the invention have been characterized in the characterizing parts of the claims.
In connection with the explanation of the invention a subscriber device means terminal devices connected to telecommunication networks and data transfer networks, such as e.g. telephones connected to fixed telephone networks, mobile stations connected to mobile communication networks and for example terminal devices connected to the Internet-network. A subscriber device also means servers connected to telecommunication networks and data transfer networks, such as telephone exchanges and servers offering services through the Internet-network providing services to the users of telecommunication networks and data transfer networks.
In other words, a subscriber device means all the parts of a network with which a telecommunication terminal device (e.g. a telephone) or a data communication terminal (e.g. a computer) can communicate over a telecommunication network or a data transfer network.
In connection with the explanation of the call transfer system according to the invention a call means in a broad sense the transfer of information between two terminal devices over telecommunication connections and data transfer connections, either to one direction or to both directions. In other words, the transfer of information comprises in addition to calls also facsimile messages, GSM short messages and e.g. the downloading of WWW (World Wide Web)-pages over telecommunication networks and data transfer networks.